This invention relates to an automatic bonding machine and more particularly to such a machine in which a video scanning head, traversable with the bonding head, scans a workpiece to be bonded, such as a semiconductor chip, prior to bonding thereby to obtain a basis for adjusting bonding position coordinates.
In bonding systems developed heretofore, various schemes have been proposed for optically scanning the workpiece prior to performing the bonding operations and for correcting any misalignments which may be so determined. Typically the image of the semiconductor chip is, in effect, compared with a mask which represents the chip or selected features thereon. The chip is then moved in response to the signal so generated in a manner so as to reduce the misalignment to an acceptable level. Examples of such systems are disclosed in U.S. Pat. Nos. 3,679,820; 3,814,845; 3,899,634; and 3,903,363. The mechanical implementation of such systems, however, is relatively complex and is a source of maintenance problems as well as of high initial cost. Likewise, the control circuits for such systems have typically involved a large number of special purpose, hard-wired signal logic circuits and analog computational circuits for processing the measured information and effecting the desired motions in reponse thereto.
Among the several objects of the present invention may be noted the provision of an automatic bonding machine of improved throughput and accuracy; the provision of such a machine which is of simplified and highly reliable mechanical construction; the provision of such a machine which, to a high degree utilizes standard and general purpose control logic elements; the provision of such a machine which is easily set up; and the provision of such a machine which is reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafer.